Small-scale variations of the recent accumulation rate in Central Dronning Maud Land, Antarctica

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Anschütz, H. , Eisen, O. , Steinhage, D. , Oerter, H. and Scheinert, M. (2006): Small-scale variations of the recent accumulation rate in Central Dronning Maud Land, Antarctica , International Symposium on Cryospheric Indicators of Global Climate Change. Cambridge, England 25 August 2006. .
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A major focus of the VISA project (validation and interpretaion of satellite data in Antarctica) is an enhanced knowledge of the ice-mass changes in Antarctica and validation of new satellite data with detailed groundborne measurements.We present a spatial and temporal analysis of accumulation data from the Antarctic expedition VISA-Ground 2003/2004 on the Potsdam Glacier in Dronning Maud Land, Antarctica. High-frequency GPR profiles of a total length of ca. 100 km were carried out along and perpendicular to the main glacier flow line in order to detect internal reflection horizons. Firn cores and snow pits were deployed at five selected locations of the GPR profiles. Three continuous reflection horizons of isochronic origin were tracked in the processed GPR data throughout several profiles. Firn-core analysis covered dielectric profiling (DEP), density measurements, and determination of the content of delta-O18. From the density profiles a cumulative mass-depth relation was established. The velocity distribution of the radar waves with depth was derived from the DEP data. With these models the tracked horizons were converted from travel time to depth and to cumulative mass, respectively. Annual-layer counting of 18O peaks yielded an age-depth relation that was used for dating two of the horizons. Combining the data sets allows us to determine the mean annual accumulation rate and its variation in the investigation area. The accumulation rate shows a high spatial variability with pronounced maxima and minima, with a mean of 143 kg m-2 a-1 with a standard deviation of 47%. This is less than the value of 200-250 kg m-2a-1 reported before in this region. These features can at least partly be explained by the surface topography and the surface slope indicating that windborne redistribution of snow significantly contributes to the accumulation.Generally, the accumulation decreases along the main flow line in the direction of glacier flow, indicating an ablation area further downwards. Our results provide new insight in local featuresinfluencing the accumulation rate in this area and can be used to validate satellite data aiming at the temporal and spatial variation of different physical variables being related to climatic conditions.

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